A continuing goal in integrated circuitry design is to make ever denser, and therefore smaller, circuit devices. This results in thinner layers and smaller geometries. Further, new deposition techniques and materials are constantly being developed to enable circuit devices to be made smaller than the previous generations. Additionally, circuit design sometimes fabricates the devices to be substantially horizontally oriented relative to an underlying substrate, and sometimes substantially vertically oriented.
One common integrated circuit device is a field effect transistor. Such includes a pair of source/drain regions having a semiconductive channel region received operably therebetween. A conductive gate is received operably proximate the channel region, and is separated therefrom by a gate dielectric. Application of a suitable voltage potential to the gate enables current to flow between the source/drain regions through the channel region, with the transistor being capable of essentially functioning as a switch.
The source/drain regions of a field effect transistor typically include semiconductive material which has been doped with a conductivity enhancing impurity of a first and/or second conductivity type. Such dopant impurity might be intrinsically provided during the fabrication of the material from which the source/drain region is fabricated, or subsequently for example by suitable gas phase diffusion or ion implanting. The conductivity type (n or p) of the transistor is determined/designated by the conductivity type of highest dopant concentration portion of the source/drain regions. Specifically, p-channel or PMOS devices have their source/drain highest dopant concentration of p type, and n-channel or NMOS devices have their source/drain highest dopant concentration of n type.
Regardless, the dopants as initially provided are eventually subjected to a high temperature dopant activation anneal to impart desired and necessary operating characteristics to the source/drain regions. However, some present and future generation conductive gate materials are/will be comprised of elemental-form metals, alloys of elemental metals, and conductive metal compounds. Such materials can be adversely affected by the typical temperatures and times required to achieve dopant activation by anneal. For example, certain metal materials (i.e., titanium, titanium nitride, molybdenum silicide, nickel silicide, titanium silicide, and cobalt silicide) are thermally unstable and result in stress/strain induced stacking faults or react with the dielectric when subjected to the high temperature anneals typically required to achieve dopant activation.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.